Retransmitting apparatus for converting interrupted telegraphic modulated signals into telegraphic signals without interruptions

ABSTRACT

A telegraphy retransmitter receives bipolar modulated signals interrupted by telegraphic modulation equipment and retransmits the bipolar modulated signals without the interruptions. The retransmitter employs polarity sensitive transistor switching circuits and a holding circuit for maintaining the desired level of the bipolar signal during the period of the interruptions, so that the period of interruption is effectively eliminated.

United States Patent [151 3,643,026

Teurnicr Feb. 15, 1972 [54] RETRANSMITTING APPARATUS FOR 7 3,073,971 1/1963 Daigle ..328/58 CONVERTING INTERRUPTED 3,180,935 4/1965 Weaver TELEGRAPHIC MODULATED SIGNALS INTO TELEGRAPHIC SIGNALS WITHOUT INTERRUPTIONS Inventor: Roger Teurnier, Rueil-Malmaison, France C.I.T. Compagnle lndnstrlelle des Telecommunications, Paris, France Filed: Dec. 23, 1969 Appl.No.: 887,502

Assignee:

Foreign Application Priority Data Dec. 23, 1968 France ..180133 References Cited UNITED STATES PATENTS Monin ..178/70 R A telegraphy retransmitter receives bipolar modulated signals 3,470,482 9/1969 Kolnowski .L ..328/58X Primary Examiner-Kathleen l-l. Clatfy Assistant Examiner-William A. llelvestine Attorney-Craig, Antonelli and Hill ABSTRACT interrupted by telegraphic modulation equipment and retransmits the bipolar modulated signals without the interruptions.

The retransmitter employs polarity sensitive transistor switching circuits and a holding circuit for maintaining the desired level of the bipolar signal during the period of the interruptions, so that the-period of interruption is eflectively eliminated.

l0 Clslms, 5 Drawing Figures RETRANSMITTING APPARATUS FOR CONVERTING INTERRUPTED TELEGRAPIIIC MODULATED SIGNALS INTO TELEGRAPIIIC SIGNALS WITHOUT INTERRUPTIONS The invention relates to a modulation retransmitter, more particularly a telegraphic modulation retransmitter, which receives at the input a modulation (for example bipolar modulation), in which the elementary signals may be affected by some deformation, and which retransmits this modulation (for example in single polar current) with elementary output signals reshaped in accordance with their theoretical curve.

It is known that bipolar current telegraphic modulation appears in the form of signals formed by the combination of several pulses, either negative or positive with respect to ground, the center point of the telegraphic battery.

The device according to the invention makes it possible to restore at the output a voltage close to ground for positive polarity at the input, and absence of output polarity for a negative polarity at the input, the converse arrangement being obviously selectable without modifying the principle of the invention.

According to the theoretical trace of bipolar modulation signals, there is no passage of time between a moment of a certain polarity and a moment of opposite polarity; now, in practice a passage of time could not be zero without giving rise to a short circuit between the two terminals of the battery.

In fact, the passage of time from one polarity to the other, may also be called break time and which corresponds to a time in which no polarity is retransmitted, is not negligible; for example, for a telegraph relay, the passage of time from one contact to the opposite contact may be of the order of 1 millisecond. Similarly, the design of the transmitting device of some teleprinters provides a break time not only between two consecutive moments of different polarity, but also between consecutive moments of the same polarity.

It is clear that independently of the distortion of signals caused by their transmission, a systematic deformation is involved, due to the very fact of their mode of generation.

It is the aim of the present invention to remedy these disadvantages by providing a device which supplies output signals reshaped according to their theoretical curve.

The retransmitter device according to the invention is characterized more particularly in that it comprises a line polarity detection device and an output device having a time constant, maintaining the output state constant for a certain time after the disappearance of the input polarity.

According to one feature of the invention, the device comprises substantially four transistors, a capacitor and resistances, two transistors being assigned, for example, to the detection of positive line polarity, one transistor being assigned to the detection of negative line polarity, and one transistor being assigned to the output signals, the capacitor enabling a time constant to be obtained in the change of state of the output transistor.

According to another feature of the invention, the detection of a negative line polarity produces, on the one hand, blocking of the output transistor and, on the other hand, rapid discharge of the capacitor; during the break following the polarity, the output transistor remains blocked and the capacitor remains discharged, all the detection transistors being then blocked.

Other features of the invention will appear from the following description of an embodiment of the invention given as example, by no means restrictive, with the aid of corresponding drawings, in which:

FIG. 1 shows a theoretical trace of bipolar modulation for a code combination;

FIG. 2 shows the real trace of bipolar modulation of the same combination obtained with the transmission device of certain teleprinters;

FIG. 3 shows a real trace of single polarity modulation of a retransmitter device in which the output control depends directly on one of the input polarities;

FIG. 4 shows the real trace in single polarity modulation obtained with the device according to the invention;

FIG. 5 shows an electric circuit diagram of a device according to the invention.

It is assumed, by way of example, that FIG. 1 relates to a telegraphic code combination comprising three positive mo ments M1, M2 and M3 and two negative moments M4 and M5; in addition the start, always negative, and the stop, always positive. The whole of the seven moments corresponds to a character of the international telegraph code. In bipolar operation, the top horizontal line corresponds to positive polarity of the telegraph battery, the bottom horizontal line corresponds to negative polarity of the telegraph battery, the middle horizontal line corresponds to zero ground potential of the middle point of the battery. The trace shown in FIG. I is a theoretical trace since at the same instant, t for example, the line is simultaneously positive, negative or at zero potential, which is obviously impossible. In fact, if the line is sometimes connected to negative polarity by means of a flexible contact blade, there is a certain nonnegligible time of travel from one contact to the other; during this time of travel the line is therefore not connected to any polarity and is therefore at earth potential by its other end.

FIG. 2 is a real trace of the modulation received in FIG. 1. It will be seen that the vertical line 1 determines the passage to negative and the vertical line 2 the return to positive, the effective duration between the time t (positive) and the time t:, (negative) being effected by means of a nonnegligible time 1 during which the line is at zero potential. Similarly, the return to positive of the time I, is effected by means of a nonnegligi ble time during which the line passes through zero potential again. The times t and t represent the time taken by the moving blade contact to travel from the positive contact to the opposite negative contact. In telegraph relays, when the movable armature has been deflected by the effect of the change in direction of the current in the coil, a permanent magnet keeps it in its new position until a fresh reversal of current in the coil brings the movable armature into the opposite position. If there are several successive moments of the same sign, the armature thus remains in fixed position on the last polarity received. However, a break time, such as or which exists only because there is a change in the line polarity, is produced because of the electromechanical design of certain teleprinters, even when there is no change in polarity. Thus, this is the case of the break time t for example, situated between the positive times t, and t FIG. 2 is therefore quite appreciably different from the theoretical trace of FIG. 1.

FIG. 3 again shows the same modulation as in FIG. I but with single polarity operation, that is to say, the upper horizontal line represents the time intervals during which the transmission line is connected to a weak polarity p close to ground, while the lower horizontal line represents the time intervals during which the transmission line is connected to positive or negative polarity originating from the utilization circuit. The polarity assumed here is negative polarity, but this choice is not obligatory. If the output control of the retransmitter device depends directly on the input polarity (positive, for example) all the disconnections are interpreted as the opposite polarity (negative, for example). The result is a distortion of the signals, due to spread of the negative moments (for example). On the other hand, there are obviously breaks between consecutive moments of the same polarity.

FIG. 4 shows single polarity modulation such as is obtained with the device according to the invention. The break times received at the input of the double current device have no repercussion on the single current output; to obtain this result, the change in output polarity must be controlled only by a change in polarity at the input and not by the break in polarity of the preceding moment.

In the embodiment shown in FIG. 5, the bipolar signals ar rive at the input E by a line I... They leave the device again by an output S and are utilizable by a load impedance R which may represent any receiving element.

Successively in series with the line L are the input E, are a diode D and a diode D the end of the line opposite to the input being grounded. The diodes D, and D are connected in emitter negative with respect to its base, remains blocked, and consequently so does the transistor T Transistor T,, on the contrary, having its emitter grounded and its base negative,

' becomes conducting. The resistance R being of fairly low of D the cathode of the diode D is also connected to the value, the capacitorC is rapidly discharged through R D, and emitter of a transistor T whose base is connected to the Tr n i z- Ground Potential across T211), 4 a and 5 is anode of D,; the bases of T and T at a common point on the thus connected to the base of transistor T since the emitter of line, are therefore at the same potential. The transistors T and T is negative with respect to the base, transistor T is blocked. T are of PNP-type. The collector of T is connected to the The output S therefore assumes negative polarity across the base of a transistor T of NPN-type, through a resistance R impedance R, of the utilization circuit. the base of T being also connected to negative polarity In the time through a resistance R The emitter of T is connected The time t, isabreak time, during which the line L does not directly to negative polarity and the collector of T is conreceive any polarity, either positive or negative. Transistors T nected through a diode D to a common point M. At point M and T remain blocked; transistor T is blocked. Transistor T two circuit branches are connected; the first formed by a reremains blocked. The output S, therefore, continues to be sistance R whose end N is connected to one plate of a capacinegative across the impedance R, Capacitor C is kept tor C, whose other plate is grounded; the second branch condischarged by the circuit R R R and ground. nects the point M to the base of a transistor T of PNP-type In the time t through a resistance R the base of T being also grounded As in the time 1,, the line L is at positive polarity. In a through resistance R The collector of the transistor T is conmanner similar to that occurring in the time I transistors T, nected to the point N through diode D and resistance R,,. and T become conducting, transistor T is blocked. Capacitor Finally, the emitter of transistor T is connected to a slightly C is rapidly charged through resistance R and diode D renegative bias voltage p; its collector, connected directly to the i tan e R being rather low. Transistor T becomes conductoiiipui has negative P y across the 103d impedance D ing, its base assuming a negative potential in the circuit The operation of the device just described is as follows: f r d b T3 D3, R5 and R6. Th output 3 b i ll It is assumed, for example, that the device according to the sumes h bi p f h emitter f T invention receives a bipolar modulation according to FIG. 2, I h i that is to say, the operation will be described at the different Th i i a b k i Transistors '1 d T are times 'lv 7' blocked; transistor T remains blocked. The capacitor C is hi the time discharged through the resistances R R and R and during its The iihe L is at Posiiive P The diode 1 appearing in discharge maintains transistor T conducting. This state is reverse characteristic, that is to say with a high internal remaintained beyond the normal break thug The output 5 sistance a weak reverse ehh'eht passes thfeugh h 'e Di therefore, retains during the break the potential p which it had and, practically, the potential of the portion of line situated during the preceding time [5. between the two diodes is positive with respect to ground. The In the time transistor T having its emitter at the telegraphic positive The line being at positive potemial, transistors TI and Ta poiarhyiwhieh is Positive with respect 9 the baseyheeeihes become conducting, transistor T is blocked. Capacitor C, conducting, but the transistor T having its base positive with 4 artly discharged, is recharged rapidly through the resistance l'espeet e the emitter, 'he e The diode D 2 is R and diode D Transistor T is maintained in the conducting ducting, its anode being positive with respect to its cathode. State by the circuit consisting of T3, D37 R5 and R8. The Output T base of trahsletor due to e voltage e e m e S, therefore, during the time t-,, retains the slightly negative sistahees R1 and assumee e h' petehhei lmermedlete potential which it had during the preceding times and between ground and negatiye polarity. This potential, being Finally the following table may be drawn up less negative than that to which the emitter of T is connected,

Time t1 Time t1 Time t Time t4 Time 1:; Time ti Time t1 Output S potential p Potential 1).. Potential across R Potential across B Potential 1).. Potential p. Potential p.

renders transistor T conducting. The capacitor C is charged which corresponds exactly to the curve shown in FIG. 4. through the diode D and the resistance R On the other hand, It will be seen that this curve has the same profile as the the base of transistor 4 assumes 3 Twin negative Potential theoretical curve of FIG. 1; however, the upper horizontal line owing to th ol ge drops in lhe resistances 5 and e- The of FIG. 1, which represented the telegraphic positive, in FIG. voltage of the base being negative with respect to the emitter, 4 represents a bias potential p, and the lower horizontal line, iiaiisisioi' T4 becomes cohduciihg- The output 5 therefore which in FIG. 1 represented the telegraphic negative, in FIG. 4 Shines a Piehiiai y Close to P- represents the negative polarity across the utilization re- In the time t,: sistance Rb The time '2 is a break time when, coiisequemiy, the line It is obvious that it will not be going outside the scope of the does not receive y Poiaiiiy, either p i or f invention to use elements giving equivalent results, in particu- Ti'ahsisioi's i T8 hiocked; transistor T2 femaihs lar to use transistors of opposite type combined with another hiocked' The capachof C dilscharged across the resietahees orientation of the diodes and supplies. Similarly, reversal of R5 h and ehnhghs discharge keeps the transistor the polarities on the output curve of the device obviously conducting. The time constant is calculated such that this remainswithinthescopeoftheinvemiom12 state persists beyond the normal break time, the resistance R Tclaim; bein of fairl hi h value for this ur ose. The out ut S therei T, J fore eetains the p otential p which h d during the time t e epparams for rehansmmmg blpolet In the time [3: contains interrupted portions, the voltage level of said inter- The line L is at negative polarity The diode D1 is in forward 7 rupted portions being difierent from the voltage levels defincharacteristic but the diode D is in reverse characteristic, that is to say, with a high internal resistance; a weak reverse current passes across the diode D, and, practically, the potential of the portion of line situated between the two diodes is very close to the negative of the line. Transistor T having its ing the amplitudes of the bipolar signal comprising:

first means for receiving said bipolar signal in its interrupted form; second means responsive to said first means for maintaining the voltage level of the bipolar signal, immediately preceding said interrupted portion, for the duration of said interrupted portion, thereby eliminating the interruption; and 1 third means responsive to said'second means for delivering said bipolar signal at an output with said interrupted portion of said bipolar signal removed, so that said signal varies between only two levels defining the amplitude of the retransmitted bipolar signal.

2. An apparatus according to claim 1, wherein said second means includes a polarity sensitive transistor circuit, connected to said third means and responsive to the polarity of the received interrupted signal, for eliminating the interrupted portion from said bipolar signal.

3. An apparatus according to claim 2, wherein said transistor circuit includes a first and second transistor switching circuit, a holding circuit and a third transistor switching circuit, said first and second transistor switching circuits providing a charging and discharging path respectively, for said holding circuit and wherein said third transistor switching circuit is connected to and controlled by said holding circuit through a discharge circuit having a time constant greater than the duration of the interrupted portion of said bipolar signal.

4. An apparatus according to claim 2, wherein said first charging diode, providing a charging path to said holding circuit.

6. An apparatus according to claim 3, wherein said second transistor switching circuit is connected through a discharging diode to said holding circuit providing a discharge path from said holding circuit.

7. An apparatus according to claim 4, wherein said transistor circuit includes a first and second transistor switching circuit, a holding circuit and a third transistor switching circuit, said first and second transistor, switching circuits providing a charging and discharging path, respectively, for said holding circuit and wherein said third transistor switching circuit is connected to and controlled by said holding circuit through a discharge circuit having a time constant greater than the duration of the interrupted portion of said bipolar signal.

8. An apparatus according to claim 7, wherein said first transistor switching circuit is connected through a charging transistor and a charging diode to said holding circuit, providing a charging path to said holding circuit.

9. An apparatus according to claim 7, wherein said second transistor switching circuit is connected to a discharging diode, providing a discharge path from said holding circuit.

10. An apparatus according to claim 8, wherein said second transistor switching circuit is connected through a discharging i diode to said holding circuit, providing a discharge path from 2 said holding circuit. 

1. An apparatus for retransmitting a bipolar signal, which contains interrupted portions, the voltage level of said interrupted portions being different from the voltage levels defining the amplitudes of the bipolar signal comprising: first means for receiving said bipolar signal in its interrupted form; second means responsive to said first means for maintaining the voltage level of the bipolar signal, immediately preceding said interrupted portion, for the duration of said interrupted portion, thereby eliminating the interruption; and third means responsive to said second means for delivering said bipolar signal at an output with said interrupted portion of said bipolar signal removed, so that said signal varies between only two levels defining the amplitude of the retransmitted bipolar signal.
 2. An apparatus according to claim 1, wherein said second means includes a polarity sensitive transistor circuit, connected to said third means and responsive to the polarity of the received interrupted signal, for eliminating the interrupted portion from said bipolar signal.
 3. An apparatus according to claim 2, wherein said transistor circuit includes a first and second transistor switching circuit, a holding circuit and a third transistor switching circuit, said first and second transistor switching circuits providing a charging and discharging path respectively, for said holding circuit and wherein said third transistor switching circuit is connected to and controlled by said holding circuit through a discharge circuit having a time constant greater than the duration of the interrupted portion of said bipolar signal.
 4. An apparatus according to claim 2, wherein said first means includes a pair of polariTy sensitive diodes connected to said polarity sensitive transistor circuit.
 5. An apparatus according to claim 3, wherein said first transistor switching circuit includes a charging transistor and a charging diode, providing a charging path to said holding circuit.
 6. An apparatus according to claim 3, wherein said second transistor switching circuit is connected through a discharging diode to said holding circuit providing a discharge path from said holding circuit.
 7. An apparatus according to claim 4, wherein said transistor circuit includes a first and second transistor switching circuit, a holding circuit and a third transistor switching circuit, said first and second transistor, switching circuits providing a charging and discharging path, respectively, for said holding circuit and wherein said third transistor switching circuit is connected to and controlled by said holding circuit through a discharge circuit having a time constant greater than the duration of the interrupted portion of said bipolar signal.
 8. An apparatus according to claim 7, wherein said first transistor switching circuit is connected through a charging transistor and a charging diode to said holding circuit, providing a charging path to said holding circuit.
 9. An apparatus according to claim 7, wherein said second transistor switching circuit is connected to a discharging diode, providing a discharge path from said holding circuit.
 10. An apparatus according to claim 8, wherein said second transistor switching circuit is connected through a discharging diode to said holding circuit, providing a discharge path from said holding circuit. 